A cooling apparatus which circulates cooling water in order to cool and/or warm an engine is known heretofore. For example, a Patent Literature 1 discloses a cooling apparatus in which an engine water pipe which passes through the engine and a bypass water pipe which bypasses the engine are connected via a valve.
The cooling apparatus disclosed in the Patent Literature 1 uses single valve to change a flowing aspect of the cooling water. Therefore, if the valve has failure (the valve is out of order), the flowing aspect of the cooling water may be likely different from a desired aspect. Thus, in the cooling apparatus which is provided with the valve, it is preferable to determine (judge) whether or not the valve has the failure. Incidentally, the Patent Literature 1 discloses logic which determines that the valve has open failure (namely, failure in which a state of the valve remains to be a valve open state against a valve close request) which is one example of the failure of the valve if there is a large difference between an estimated value of engine water temperature which is estimated from integrated intake airflow of the engine and an actual value of the engine water temperature.
Patent Literatures 2 and 3 are presented as a background art relating to the present invention.